Large open top containers are commonly used to transport loose materials such as construction debris or refuse to landfills or other dumping locations. These containers are often transported on a roll-off truck that has the capability to pick up and off-load the container at desired locations. The tops of such containers are typically open to facilitate loading. In many places, laws and regulations require the tops of such containers to be covered before they can be transported on public roadways so that material from the container cannot be blown out of the containers. Even where there are no laws regarding covering a load, it is beneficial for the driver to cover the load in order to reduce the possibility of damage to other property from rocks or other debris that might escape from the container. These containers typically have a rectangular top opening. The size of these containers may vary, with many containers ranging from 16 to 24 feet in length and 4 to 8 feet in height. It is common for any one roll-off truck to carry a number of different sizes of these containers.
Placing a tarp or cover on a container manually is both time-consuming and expensive. The need for a covering apparatus to accommodate various container sizes that would automatically deploy the cover or at least simplify and speed up the covering process became apparent some time ago.
Several systems have been proposed to address the need to cover open top containers during transport. One approach has been to provide a spring-loaded spool, mounted to the front of the truck, that moves up and down on a pedestal to suit the height of the container. The driver can then pull the cover off of the spool out over the container opening like one would pull a window shade. Although this semi-automatic covering method is better than manual covering, it is still difficult and time consuming, and requires the driver to fasten the end of the cover that was pulled off of the spool to the container. Many of the prior art devices that automate the covering process are similar to the semi-automated process described above, but have a pivoting arm secured to the truck or truck body on each side of the container. These arms pull the end of the cover over the container. Sometimes these arms are spring-loaded to pull the cover toward the rear of the container as the cover is unrolled from the motor-controlled roller at the front of the container. Sometimes the roller at the front of the container is spring-loaded to roll the cover up on it, and the arms are controlled by a hydraulic cylinder or other suitable mechanism to pull the cover over the container. Further, some of the prior art devices have a spring-loaded roller with the cover rolled onto it and attached to the arms, with the other end of the cover attached to the truck just behind the cab. As the arms pivot, the spool of material is pulled from front to back over the top of the container, thereby unspooling the material so that it lies over the open top, effectively covering the container.
One of the greatest challenges in the covering mechanisms is to provide the ability to adapt to various container lengths and heights. One approach to these challenges is to provide for a telescopic arm pivotally attached to either the container itself or the truck that transports the container, such as disclosed in U.S. Pat. No. 4,874,196 to Goldstein et al. and U.S. Pat. No. 5,803,528 to Haddad, Jr. However, the use of telescopic arms tends to be generally more expensive to fabricate and more difficult to maintain than employing arms in a pivoting motion in especially harsh environments to which these covering systems are commonly.
A second approach to accommodating the various container sizes has been to provide an arm composed of two pivotally connected sections such as disclosed in U.S. Pat. No. 5,292,169 to O'Brian. However, when hauling a container that has a is shorter length, this type of covering mechanism may require the end of the arm that supports the spool of covering material to hang over the back of the container when the cover is applied. As a result, the end of the arm is unsupported during transport of the container, and all of the shock loads or dynamic loads that occur are applied directly to the base of the arm. Further, this could put large loads on the cover itself, potentially causing premature failure. These loads could be significant and could require over design of the base structure, with its accorded additional weight, and/or a reduced operating life of the mechanism. Further, the end of the arm is exposed to potential damage because it is the rearmost point on the truck when the cover is applied.
Another disadvantage of both the sliding and pivoting types is that two separate motions control the roller position, the rotation of the base arm and either the extension or rotation of the outer arm. This is a substantial problem if the rolled up cover is stored between the truck cab and the container. To deploy the cover, the roller must initially move in a substantially vertical line from its stored position in between the cab of the truck and the top of the front wall of the container as the container is being covered. Often the space in between the cab and the container is small and any deviation from the vertical path may result in damage to the covering mechanism, the cab of the truck, or the container. One partial solution to this problem has been to mount the stored spool of covering material at or above the top of the cab of the truck. However, this mounting position necessitates a tall support structure for the spool of covering material that at least partially obstructs the view through the back window of the cab. Additionally, a tall support structure potentially prevents adequate coverage of the front edge of the container when the containers have a shorter height.
A further disadvantage of the pivoting type of the prior art is that in covering short containers, with the roller placed on the rearmost top edge of the container, the base arm would stick up considerably above the top of the container, increasing the possibility of damage to the covering apparatus from tree limbs as the container is being transported.
A further disadvantage of the prior art is that, in the stowed position, at least portions of the arms are substantially above the bottom of the container. Thus, as the container is rolled on and off the vehicle, components of the container, such as hinges and latches, which are typically positioned at the maximum width of the container, are more likely to hit and damage the covering mechanism.
Another problem with manual covering of a container, and with certain semi-automatic covering systems is the risk of injury. When items in a container project upward beyond the top of the container, the operator may need to climb up on the container and/or load to cover the container, or ensure that the covering is able to extend over the items projecting upward out of the container. The risk lies not only in climbing up high off the ground, but also in the parts of the load that could cut or injure the operator. Also, in some prior art container covering systems, it is difficult for the cover to get over such projecting loads, particularly the types of container covering systems that extend linearly over the container.